Anodizing apparatus



July 2, 1968 RUSCH ET AL ANODIZING APPARATUS 4 Sheets-Sheet 1 Filed Aug.24, 1964 lwvamons RONALD L. RUSCH CHARLES H.ORDING KW V ATTYS.

ly 2, 1968 R. 1.. RUSCH ET AL 3,391,073

ANODIZING APPARATUS 4 Sheets-Sheet 2 Filed Aug. 24. 1964 201 33 37 rINVENTORS Romw L. RuscH CHARLES H. ORDING July 2, 1968 R. L. RUSCH ETAl. 3,391,073

ANODIZING APPARATUS Filed Aug. 24, 1964 4 heet 5 I22 B 33 F 45INvaN-roR's RONALD L. RuscH CHARLES H. 02mm;

:1 ww 'vm A'rrvs.

July 2, 1968 Filed Aug. 24, 1964 R. L. RUSCH ET AL.

ANODIZING APPARATUS 4 Sheets-Sheet 4 RONALD L. RuscH CHARLES H. GnomeUnited States Patent 3,391,073 ANODIZING APPARATUS Ronald L. Rusch,Northbrook, and Charles H. Ording,

Palatine, lll., assiguors to Aluminum Coil Anodizing Corporation, FoxRiver Grove, Ill., a corporation of Illinois Filed Aug. 24, 1964, Ser.No. 391,617 11 Claims. (Cl. 204-202) ABSTRACT OF THE DISCLOSURE Acontinuous anodizing apparatus having a titanium or zirconium endlessconveyor belt on which are mounted a multiplicity of removable striparticle holders, each holder supporting a multiplicity of articles to beanodized, said articles being moved by the apparatus through theanodizing electrolyte by the endless belt in a predetermined tortuouspath so that the position of each article is repeatedly varied about 90each direction from the vertical during the anodization.

The present invention relates to apparatus for anodizing metalparticles, such as aluminum. (The anodizing process is generally onewherein the surface of a metal, such as aluminum, is oxidized byimmersing the metal connected to a source of positive voltage in an acidelectrolyte such as sulfuric acid.)

In the anodizing process as heretofore practiced, the articles to beanodized were generally placed in metal baskets or racks carried on aconveyor. The conveyor moved the article carrying baskets or rackssequentially over an open-top tank containing the anodizing electrolyteand then lowered the baskets or racks into the tank for the requiredperiod after which the baskets were raised and then carried to othertanks containing various chemicals for rinsing, dyeing, and/ or sealingthe anodized surfaces of the articles. The baskets or racks carrying thearticles to be anodized must be electrically connected to the positiveterminal of a source of direct current voltage so that the articles tobe anodized have a positive voltage thereon through their contact withthe baskets or racks. In general, the equipment which has been used foranodizing articles is similar to the equipment generally used inelectroplating articles. In the electroplating process, the articles tobe plated are connected to the negative terminal of a source of directcurrent voltage and metal is deposited by a reduction process upon allof negatively charged metal surfaces within the electrolyte. In suchcase, for example, the basket or rack carrying the articles would beplated along with the articles involved. It is generally impractical,therefore in electroplating equipment to physically immerse the conveyorequipment carrying the baskets or racks into the electrolyte, althoughsuch immersion was suggested from time to time. It was perhaps notappreciated by the people who designed anodizing equipment that thereare important advantages to immersing the conveyor equipment in theelectrolyte without the accompanying disadvantages, since the anodizingprocess, unlike the electroplating process, will not affect all immersedmetal surfaces having the same charge as the articles to be anodized.Thus, titanium and zirconium will not be anodized or corroded whenimmersed 3,391,073 Patented July 2, 1968 in an aluminum anodizingelectrolyte like sulfuric acid with a positive voltage applied thereto.

The type of equipment heretofore used in conveying articles to beanodized to the open-top electrolyte containing tanks, as aboveindicated, suffers from a number of disadvantages. In the first place,the conveyor equipment and the controls therefor which intermittentlycaused longitudinal and then transverse up and down movement of thebaskets required frequent replacement. Also, such equipment, for reasonsto be explained, frequently did not produce a uniform finish,particularly where imperforate cup-shaped articles were involved whichbecame inverted in the racks or baskets.

The present invention represents a marked improvement in anodizingequipment. Thus, in the anodizing equipment of the present invention tobe described, the articles to be anodized are carried into and out ofthe open-type electrolyte containing tank by a positively chargedcontinuously longitudinally moving, endless conveyor which passesdirectly into the electrolyte. The positively charged conveyor is madeof a material like titanium which is not affected by the electrolyte andthe guide supports for the conveyor located within the electrolyte arepreferably insulated from the voltage source involved so that it can bemade of a material like stainless steel which is not affected by theanodizing electrolyte if, kept electrically neutral. The conveyor, ismost advantageously an endless belt made of sheet metal, which moves ina steeply undulating path in the electrolyte so that there is a maximumpath length for a tank or given length to minimize floor spacerequirements, and so that the articles are turned over appreciableangles as the direction of the path reverses in the electrolyte toprevent the collection of gas pockets in imperforate cup-shaped articleswhich will prevent the formation of a uniform anodized coating thereon.

Other features of the invention relate to the manner in which thearticles are attached to the belt conveyor and are automatically removedtherefrom. For example, the articles are preferably carried on springmetal clips attached to carrier strips or bars which are readilyremovable from the belt. The equipment is thus usable with differentarticles by merely removing one set of carrier strips and substitutinganother set with differently sized or shaped clips. Some other featuresof the invention relate to the construction of roller carrying frameassemblies which guide the belt conveyor in and out of the various tanksinvolved.

The above and other advantages and features of the invention will becomeapparent by making reference to the specification to follow, the claimsand the drawings wherein:

FIG. 1 is a side elevational view of anodizing apparatus incorporatingfeatures of the present invention;

FIG. 2 is a fragmentary view of the anodizing tank portion andassociated belt supporting and guiding assembly supported therein of theapparatus shown in FIG. 1 with parts thereof shown in exploded view;

FIG. 3 is an enlarged vertical sectional view of the anodizing tankportion and associated belt supporting and guiding assembly supportedtherein of the apparatus of FIG. 2, taken substantially along the lines3-3 in FIG. 1;

FIG. 3A is an enlarged sectional view of a portion of the apparatusshown in FIG. 3;

FIG. 4 is an enlarged vertical sectional view of a portion of theapparatus shown in FIG. 1 taken substantially along the lines 4-4thereof, and illustrating the construction of a drive roller and thesupport units therefor;

FIG. 5 is a side elevational view of one of the drive roller supportunits shown in FIG. 4;

FIG. 6 is a partial horizontal sectional view through the apparatus ofFIG. 4;

FIG. 7 is a fragmentary plan view of the discharge end of the apparatusshown in FIG. 1;

FIG. 8 is a vertical sectional view of the apparatus through the portionof the apparatus shown in FIG. 7 taken along the lines 8-8 therein; and

FIG. 9 is an enlarged fragmentary sectional view through the sheet metalbelt forming a portion of the apparatus of FIG. 1.

Referring now more particularly to FIG. 1, the anodizing apparatus thereillustrated includes a series of opentop tanks into which aluminumarticles 1 shown in FIG. 3 to be anodized are sequentially carried by aunique conveyor system 2 to be described. The first tank 4 to which thearticles are carried from a loading station 3 contains a suitablealuminum cleaning non-etchant material as, for example, a non-silicatedcleaner sold under the name Redi Aluminum Cleaner No. 1, manufactured bythe Redi Chemical Co. of Barrington, Ill. Next, the articles aredelivered to a water rinsing tank 5 which rinses the cleaning material.The articles are then carried into a pair of anodizing tanks 6 and 6awhich contain a solution of sulfuric acid, the level of the acid in thetanks 6 and 6a being identified by reference numeral 7. As will appear,the conveyor system is insulated from the anodizing tanks 6 and 6a andis connected to the positive terminal of a source of direct currentvoltage. The tanks 6 and 6a are connected to the negative terminal ofthe voltage source. The articles are then delivered to a water-filledrinsing tank 8 and then to a tank 10 containing a sealing material, suchas a solution of nickel-acetate, which seals the pores of the oxidecoating resulting from the anodizing treatment in a well known manner.Following the sealing operation, the articles 1 are delivered to adrying tank 12, which may be a well known type of tank containingsuitable sources of heat, such as gas burners, for drying the articlesinvolved. After removal from the tank 12, the articles are delivered toa discharge station 14 where the articles are automatically dischargedin a manner to be explained. If desired, additional treatment tanks maybe added to the apparatus shown for carrying out additional operation,such as dyeing and the like. The various steps in the anodizing processjust described are exemplary only.

One of the important aspects of the present invention is the manner inwhich the articles 1 are carried into and out of the various tanks. Aspreviously indicated, it was common in anodizing apparatus to utilize arather complex conveyor system where the articles were carried in racksor baskets which are first longitudinally moved into position over agiven tank and then dropped into a tank where the racks or basketsremain in a stationary condition for a given period after which thebaskets or racks are raised out of the tank and then movedlongitudinally over the next tank. In the preferred form of theinvention, the conveyor system 2 most advantageously is an endless beltof titanium or zirconium sheet metal which is rugged and is not corrodedor anodized by any of the liquid materials in the tanks 4, 5, 6, 6a, 8and 10. The belt 20 is continuously advanced through the various tanksthrough a steeply undulating path. Particularly in the anodizing tanks 6and 6a, the steeply undulating path comprises a number of long verticalsegments connected by short horizontally curving segments occurring whenthe direction of movement of the belt is reversed. Such a configurationhas a number of important advantages. In the first place, relativelylong dipping operations can be effected with a continuous movement ofthe belt 20 with modest longitudinal tank dimensions, so that the tanksrequire a minimum of floor space. In the aluminum anodizing processbeing described, it can be seen that the total vertical path length inthe tanks 6 and 6a is quite substantial relative to the length of thetanks. In the second place, as will appear, where the articles to beanodized are placed in inverted position against the upper surface ofthe belt, any liquid collecting in the articles as they are movedthrough the electrolyte will be dumped back into the tank when the beltmoves out of the tank. Also, as the articles are varied in position inbeing carried into a new vertical path, any gas pockets which may bepresent in the articles are moved substantially about and usually escapefrom the articles, so that the anodizing electrolyte will contact allinterior as well as exterior surfaces of the articles.

Referring, for example, to FIGS. 4, 7 and 9, the endless sheet metalbelt 20 is provided with longitudinally spaced pairs of laterally spacedslits 25-25 distributed over the full length thereof. Each pair of slits25-25 form means for resiliently and removably mounting a narrow,elongated, fieXible, resilient carrier strip or bar 29. Each of thestrips has a pair of reduced projections 31-31 at the ends thereof whichfit into a pair of the slits 25-25. The carrier strips 29 can beremove-d from the belt by simply pulling the same from the slits, theflexibility thereof enabling the same to flex and shorten about atransverse axis.

The carrier strips 29 each carry a number of spaced spring metal clips33 which removably carry the cup-shaped articles 1. Each clip 33 has twopairs of upwardly and outwardly extending fingers 33a-33a, each of whichhas an inwardly curved outer end 33b. The fingers have an extentsomewhat greater then the size of the Opening of the articles 1. Theinverted cup-shaped articles 1 can, therefore, be readily applied to theclips by inverting the same and pressing the same down over the roundedends of the clips which causes the fingers to be cammed inwardly toallow the article to be telescoped over the clip and securely held on.As previously indicated, the provision of carrier strips 29 which arereadily removable from the belt 20 enables the ready substitution ofdifferent sized clips on the belt 20 for carrying various sized andshaped articles. The carrier strips 29 are attached to the outside ofthe belt 20 so that they are on the top of the upper section 20a of thebelt and on the bottom of the lower section 20b of the belt.

The lower section 20b of the belt rests upon the upper surfaces of idlerrollers 37 supported upon the vertical webs 39a-39a of I beams 39-39which form a support base for the entire apparatus. The upper flanges3911-3917 of the I beams 39-39 support the various tanks 4, 5, 6, 6a, 8,10 and 12, as well as other portions of the apparatus to be described.The anodizing tanks 6 and 6a are preferably insulated from the I-beamsflanges by layers of insulation 41 (FIG. 3) placed beneath the tanks.

As best shown in FIG. 3, each of the anodizing tanks 6 and 6a has aterminal post 42 to which is connected a conductor 43 extending to thenegative terminal of a suitable source of direct current voltage (notshown) of a magnitude, for example, in the neighborhood of from 20 to 30volts.

The lower section 2012 of the belt 20 passes upwardly around endmostbottom cylindrical drive rollers 45-45 and joins the upper section 20aof the belt at endmost upper drive rollers 45-45. The upper and lowerendmost drive rollers 45 are rotatably supported between pairs ofvertical frame side walls 47 and 48 supported in a suitable manner fromthe I-beams 39-39. Each drive roller 45 is driven by a common endlesschain 49 engaging a sprocket wheel 50 attached to a shaft 51 of theroller. The bottom section of the chain 49 passes beneath the upperflange of one of the I-beams 39 where it is engaged and guided bysprocket wheels 50" rotatably supported on the I-beam web 39a (FIG. 3).

The upper section 20a of the endless belt 20 passes around a series ofsimilar drive rollers 45 above and adjacent the ends of the varioustanks and beneath various guide rollers 52 and, in the case of theanodizing tanks, around contact rollers 52', supported in a manner to bedescribed within the various tanks. The latter drive rollers 45 havesimilar sprocket wheels 50 driven by the chain 49. At the dischargestation 14, the belt 20 passes straight down between the upper and lowerendmost drive rollers 45, but the chain 49 passes around adjustablesprocket wheels 53.

The upper endmost drive roller 45 at the discharge station has a secondsprocket wheel 50" attached thereto which is engaged by a chain 54driven by a drive sprocket wheel 55 carried on a shaft 56 which carriesanother sprocket wheel 57 engaged by a chain 58. The chain 58 is drivenby a sprocket wheel 60 carried on the shaft of a motor unit 62. Themotor unit 62 is illustrated as supported upon a support base 64 carriedupon the upper flanges 39b of the I-beams 39-39.

The various guide rollers 52 in the various tanks form part of beltsupporting and guiding assemblies 72, 74, 76, 78, 80 and 82, suspendedrespectively in the tanks 4, 5, 6, 6a, 8, or 12. A description will nowbe given of the belt supporting and guiding assembly 76 associated witheach anodizing tank 6 and 6a, it being understood that the otherassemblies have similar constructions. Corresponding elements of theseassemblies are similarly numbered.

The belt supporting and guiding assembly 76 associated with each of thetanks 6 and 6a include a pair of vertical support plates 84 and 84 whichextend downwardly into but in spaced relation to the associated tanks,as best illustrated in FIG. 3. The plates are rigidly tied together by aspacer sleeve and rod assembly 85 anchored thereto. Rotatably supportedbetween the bottom portions of the plates 84-84 are three longitudinallyspaced guide rollers 52. At least the belt contacting surfaces of therollers 52 are coated with a suitable layer 86 (FIG. 3) of insulatingmaterial like Teflon, which is not affected by the anodizing electrolyteand insulate the rollers from the voltage on the belt, and each of theguide rollers 52 has a shaft 88 which is rotatably supported in suitablebearings 90-90 secured to the support plates 84-84. A pair of transverseend walls 91-91 are secured to the end portions of the shaft 88. The endwalls have confronting axially inwardly extending flanges 92-92 which,together with the ends of the end wall projecting therebeyond, defineguideways for the upper section a of the belt passing around the bottomportions of the guide rollers. The aforesaid insulating layer 86 isapplied at least to the surfaces of guideways.

The plates 84-84 rotatably support a pair of upper cylindrical contactrollers 52' which are positioned preferably above the level of theassociated tank 6 or 6a at points between the guide rollers 52. Theupper section 20a of the belt thus passes around the bottom of each ofthe guide rollers 52 and around the tops of the contact rollers 52. (Thecontact rollers 52 are replaced by guide rollers 52 in the beltsupporting and guiding assemblies of the tanks 10 and 12.)

Each of the contact rollers 52 has a cylindrical metal outer wall 102which makes good electrical contact with the belt 20 passing therearoundover substantially the entire length of the outer wall 102. The contactroller 52 has metal end walls 104 which terminate in metal bosses 106which are electrically and mechanically connected to a shaft 108journalled in suitable bearings 110 anchored to the support plates 84-84by bolts 111. The positive terminal of the aforesaid source of directcurrent voltage is connected to the ends of the shaft 108 associatedwith each of the contact rollers 52 by a pair of brushes 112- 112 ridingupon the rotating ends of the shaft 108. The brushes 112 are carried bysuitable bus bars 114 which are connected by suitable conductors to theaforesaid positive terminal. The bearings and shaft 108 are preferablyinsulated from the bolts 111 and the support plates by suitably placedinsulation 115 so that support plates and the guide rollers 52 supportedthereon will not have any voltage thereon.

All the parts of the belt supporting and guiding assembly 76 which arecontacted by electrolyte are preferably made of stainless steel. (Thestainless steel would be corroded by the electrolyte if the positivevoltage on the belt 20 were applied thereto, hence the need for theinsulating layer 86 thereon.) The cylindrical outer wall 102 of each ofthe contact rollers 52' which contact the wetted belt 20 is alsopreferably made of stainless steel. The shaft 108 and the end walls 104of each of the contact rollers 52 as shown are not made of stainlesssteel and so, to prevent damage to these parts of the rollers bydripping acid, a suitable coating 11-6 of rubber is placed on theexposed surface of the end walls 104, the associated bosses 106 adjacentportions of the shaft 108.

Each of the support plates 84 has a pair of laterally extending wings84a-84a at the upper outer ends thereof that are anchored as by boltsand nuts or the like to a vertical flange of a pair of take-up units 122positioned at opposite ends of the associated tank. (There is a takeupunit 122 at each end of the various tanks 4, 5, 6, 6a, 8, 10 and 12.) Itis apparent that by unbolting the support plates 84-84 of any be-ltsupporting and guiding assembly, the entire assembly can be removed as aunit from the associated tank. This feature is useful for servicing theapparatus or alleviating jamming which might occur within the tanks.

Each take-up unit other than the ones at the outer ends of the endmosttanks 4 and 12 are supported on a vertical post 124 having a base 126secured in any suitable way and insulated from the upper flange 39b ofone of the I- beams 39. The outermost pairs of take-up units 122 aremounted upon the associated vertical frame plates 47 and 48. Eachtake-up unit includes a vertical bearing carrying slide member which, inthe illustrated embodiment of the invention, is provided with spacedvertical side channels 128-128 (FIG. 6) slidably encompassing spacedvertical guide edges 130-130 of the take-up unit. A screw 132 isanchored to the slide member 125, the screw passing through an upperwall 133 of the take-up unit. A nut 135 threads around the end of thescrew above the upper Wall 133 and thus, by rotating the nut 135, thescrew and the slide member 125 attached thereto is raised and lowered.Each slide member 125 has a bearing 139 for journalling one end of theshaft 51 of a drive roller 45 or the shaft 108 of a contact roller 52.(All of the take-up units except the one at the left hand end of thetank 6 support drive rollers.) By varying the elevation of the slidemember 125 and the associated drive or contact roller rotatablysupported thereon, the tension of the belt 20 can be readily varied.

Referring now more particularly to FIG. 4 which illustrates theconstruction of the drive rollers 45. Each drive roller 45 has acylindrical outer wall 149 carrying a rubber sleeve 150 which makes agood frictional contact with the belt 20, and end Walls 151-151terimnating in bosses 152-152 secured to the shaft 51. A sprocket wheel50 is fixed to the end of the shaft 51.

As previously indicated, means for automatically stripping articles arecarried on the clips 33 at the discharge station 14. This means includesa plurality of pairs of stripping fingers 156-156. The stripping fingers156 are carried on brackets 158 (see FIGS. 7 and 8) mounted on a rodassembly 159 anchored to the vertical frame plates 48-48. The strippingfingers 156 extend to a point contiguous to the top of the endmost driveroller 45 and they incline at a substantial angle extending downwardlyand outwardly away from the drive roller. Each pair of stripping fingers156-156 are spaced apart and positioned to enable one of the rows of theclips 33 to pass therebetween as the belt passes down around the latterdrive roller. The spacing of each pair of stripping fingers is, however,less than the overall width of the articles sup ported upon the clips33. Thus, as the belt 29 passes down around the endmost drive roller 45and the clips 33 move below the stripping fingers 156156, the articles 1are stripped from the clips. A pair of hold down bars 157- 157 extendover and close to the drive roller 45 to hold the carrier strips 29 downas the articles are stripped from the clips 33. The stripped articlesslide by force of gravity down the inclining upper surfaces of thestripping fingers where they finally slide olf the fingers into asuitable container or on a conveyor (not shown).

It is apparent from the exemplary apparatus shown in the drawings, thatthe present invention provides a very simple, reliable, and efficientmeans for conveying articles to be anodized into and out of the variousopen-top tanks. Also, due to the steeply undulating paths of the beltwithin the liquid of the various tanks, a maximum path length isachieved in each of the tanks with a minimum tank size. Also, the pathconfiguration of the conveyor in the anodizing tanks prevents collectionof the gas pockets which cause non-uniform anodizing in imperforatecupshaped articles. In this connection also since the cupshaped articlesare in inverted position held on the outside of the belt they willautomatically be drained of all liquid as the belt curves into ahorizontal position upon leaving each tank. Furthermore, theconstruction of the belt supporting and guiding assemblies is such thatthe equipment can be readily assembled and dis assembled for servicingand eliminating jamming and the like.

It should be understood that numerous modifications may be made in themost preferred form of the invention described above without deviatingfrom the broader aspects of the invention.

We claim:

1. In combination with an open-top tank containing an electrolyte foranodizing metal articles, a conveyor sys tem for carrying articles intoand out of the electrolyte in said tank from the top of the tank, saidconveyor system comprising: an endless conductive conveyor immune tosaid electrolyte and non-anodizable therein and having article carriersdistributed therealong for removably holding articles to be anodized,said conductive conveyor comprising an endless belt provided withlongitudinally spaced pairs of laterally spaced slots, and said articlecarriers being carried on resilient sheet metal bars each havingprojections on the ends thereof fitting into a pair of said slots andremovable therefrom by bending the bars along a transverse axis toshorten the same, means within and without said tank for guiding saidendless conveyor for continuous longitudinal movements along apredetermined continuous path which passes an article feeding stationbefore entering the open-top of said tank and an article dischargestation after leaving the open-top of said tank, means for continuouslydriving said conveyor along said path, a source of direct currentvoltage having positive and negative terminals, and means connecting thepositive terminals of said source of direct current voltage to thearticles to be anodized through said endless conductive conveyor.

2. In combination with tank means holding electrolyte for anodizingmetal articles, a conveyor system for carrying articles into and out ofthe electrolyte in said tank means, said conveyor system comprising: anendless conductive conveyor made of one of the group consisting oftitanium and zirconium immune to said electrolyte and non-anodizabletherein and having article carriers distributed therealong, said articlecarriers including means for removably holding articles to be anodized,guide means within and without said tank means guiding said endlessconveyor for continuous longitudinal movement along a predeterminedcontinuous undulating path which passes an article feeding stationbefore entering said tank means and an article discharge station afterleaving said tank means, means for continuously driving said conveyoralong said path, a source of direct current voltage having positive andnegative terminals, and means connecting the positive terminal of saidsource of direct current voltage to the articles to be anodized throughsaid endless conductive conveyor comprising a series of current carryingmembers making physical contact with said endless conveyor at a numberof longitudinally spaced points of the path of travel thereof betweenthe point of entry of the endless conveyor into said tank means and thepoint of exit thereof from the tank means, to feed current thereto at anumber of different locations between said entry and exit points.

3. The combination of claim 2 wherein said endless path is a steeplyundulating path between said points of entry and exit into said tankmeans and which path repeatedly enters and momentarily leaves theelectrolyte in said tank means, and said current carrying members makingphysical contact with said endless conductive convcyor at the pointswhere the endless conductive conveyor momentarily leaves the electrolytein said tank means.

4. The combination of claim 2 wherein said current carrying members alsoact as part of said guide means.

5. The combination of claim 4 wherein said combination current carryingmembers and guide means are rotatably mounted conductive cylindersaround the periphery of which passes the endless conductive conveyor.

6. The combination of claim 2 wherein said endless conductive conveyoris an endless sheet metal belt.

7. The combination of claim 2 wherein said endless conductive conveyoris an endless belt which has distributed across the width and lengththereof said article carriers.

8. The combination of claim 7 wherein the belt has a width somewhat lessthan the corresponding dimensions of said tank means.

9. The combination of claim 2 wherein said guide means within said tankmeans supporting said endless conveyor being immersed in the electrolyteand being a material which will not anodize in the electrolyte orcorrode therein if maintained electrically neutral, said guide meanswithin said tank means being insulated from said source of directcurrent voltage.

10. The combination of claim 2 wherein the metal articles to be anodizedare imperforate cup-shaped metal articles, said article carriersremovably hold said cupshaped articles to be anodized, and saidundulating path of said conveyor in the electrolyte following a curvewhere the angular position of the cup-shaped articles is varied as muchas 9 0 degrees to allow any entrapped air to escape to eliminate thepresence of unanodized areas.

11. The combination of claim 2 wherein said tank means includes at leastone tank, a conveyor supporting and feeding assembly raisable andlowerable as an unit in and insulated from each tank, said assemblyincluding a pair of support members extending down into said tank onopposite sides thereof, a first series of horizontally spaced rotatablemeans mounted between the bottom portions of said support members wherethe rotatable means are located in the lower regions of the electrolytein said tank,.and a second series of horizontally spaced rotatable meansmounted between the upper portions of said support members above andbetween said first series of rotatable means, said support membershaving portions extending outside said tank; support means outside saidtank supporting said portions of said support members extending outsidesaid tank; a pair of rotatable means above the level of and at oppositeends of said tank and extending generally .parallel to said first andsecond series of rotatable means and adjustably supported on said lastmentioned support means for vertical movement relative thereto and tosaid first and second series of rotatable means; and said endlessconductive conveyor passing beneath said first series of rotatable meansand around the tops of said second series of rotatable means and saidpair of rotatable means to form a steeply undulating conveyor path inthe electrolyte.

References Cited UNITED STATES PATENTS Rabezzana 204204 Jording 204297XR Smith 20428 Yeager 204202 Tuttle 204297 XR Kronsbein 204202 10Altenpohl 20428 Chapman et a1 20428 Lockwood 20428 Lloyd 20428 FOREIGNPATENTS Germany.

JOHN H. MACK, Primary Examiner.

0 W. VAN SISE, Assistant Examiner.

